The author has previously shown that it is possible to cross Mexican blind cave fish to their normal eyed surface fish ancestor. The F1 and F2 generations show intermediate forms of eye development so that this system offers the unique opportunity for elucidating the genetic control of eye deveopment as well as allowing an increased understanding of the tissue interactions involved in eye development. Work currently underway seeks to examine the structure of the lens in the intermediate forms. This is being done with light microscope, electron microscope and immuno fluorescent methods. Several different types of lenses can be seen but their relationship to normal lens development is still unclear.